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Common materials in engineering. Polymers: what they are and how they work?

Common materials in engineering. Polymers: what they are and how they work? . Michael R. Kessler. Materials Science and Engineering Department Iowa State University. Outline. What is materials science and engineering? What are polymers? Making of a polymer (demonstration)

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Common materials in engineering. Polymers: what they are and how they work?

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  1. Common materials in engineering. Polymers: what they are and how they work? Michael R. Kessler Materials Science and Engineering Department Iowa State University

  2. Outline • What is materials science and engineering? • What are polymers? • Making of a polymer (demonstration) • Properties of polymers • Conclusions

  3. Materials and Civilization • Materials have always been an integral part of human culture and civilization Timeline of Human History Stone Age Bronze Age Iron Age Today? Silicon Age(?) Polymers Age(?) Composites Age(?)

  4. What do materials engineers and scientists do? • We create new materials and improve existing materials. • Virtually every modern technology is materials-limited with respect to performance, reliability, and cost

  5. Requirements of Engineering Materials • For a given application these materials must: • Have the correct properties (for production and service) • Not fail in use • Have acceptable costs • Be compatible with environmental standards

  6. A Key Theme in Materials Science Structure Properties Performance During processing During service *From Elements of Materials Science and Engineering, L. H. Van Vlack

  7. What are Polymers • Examples of polymers and where they are used. • Often Synthetic Polymers are called Plastic. • The volume of polymers produced is three times larger than that of all metals! • Poly (many) mer (parts)  made up of molecules of very long chains.

  8. Simple Polymer (Polyethylene) Polyethylene Ethylene

  9. Analogy for the Structure of Polymers

  10. Making a Polymer (Demonstration) 50 ml distilled water 50 ml hexane 2.0 ml sebacoyl chloride 1.0 g sodium hydroxide + 3.0 g hexamethylene-diamine One drop green food coloring Nylon *nylon 6-10

  11. Properties of Polymers • Glass transition temperature (snake pit analogy) • Strength—measured in maximum stress (force per unit area) • Stiffness—measured in stress per unit strain • Damping—ability to absorb energy Properties are often temperature and rate dependent (Viscoelastic)

  12. Properties (Demonstration) Happy Ball Sad Ball • Compare the damping properties for two apparently identical polymer balls by bouncing them on the floor. • How do their damping behaviors vary with temperature? Happy Ball = Neoprene (polychloroprene) Sad Ball = Norsorex (polynorbornene)

  13. Types of Polymers Crystalline Region • Thermoplastics • Amorphous • Semi-crystalline • Thermosets Crosslinks

  14. Thank You • Please feel free to contact me with questions or comments • E-mail: mkessler@iastate.edu • URL: http://mse.iastate.edu/mkessler

  15. High School Feud Question #1 • What material property reaches a maximum at the glass transition temperature?

  16. High School Feud Question #2 • The volume of polymers produced each year is about 3 times that of metals. However, the mass of all metals produced is nearly twice that of polymers. What is the average relative density of a metal compared to a polymer.

  17. High School Feud Question #3 • If a polymer nylon rope with a radius of 2 mm fails when the tensile load is increased to 200 N? What load will cause a similar rope with a diameter of 4 mm to fail?

  18. High School Feud Question #4 • List an example of an amorphous themoplastic polymer?

  19. High School Feud Question #5 • If a material is viscoelastic, what two things are its mechanical properties dependent on?

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